Hemp composites

Hemp Compositions. Proc World Textile Congress on Polypropylene in Textiles, Huddersfield, 1996, 161. 

Hu and Lim [32] showed that PLA/hemp composites with 40% volume fraction of alkali-treated fiber had the best mechanical properties. The tensile strength and elastic modulus were 54.6 MPa and 8.5 GPa, respectively, which were much higher than those of PLA alone. The flexural strength of these composites was also higher (112.7 MPa) than that of PLA alone due to the improved interfacial adhesion between fiber and matrix. 

A Ramezani Kakroodi, Y Kazemi, and D Rodrigue. Mechanical, rheological, morphological and water absorption properties of maleated polyethylene/ hemp composites Effect of ground tire rubber addition. Composites Part B. 51,337-344 (2013). 

Seventy years ago, nearly all resources for the production of commodities and many technical products were materials derived from natural textiles. Textiles, ropes, canvas, and paper were made of local natural fibers, such as flax and hemp. Some of them are still used today. In 1908, the first composite materials were applied for the fabrication of big quantities of sheets, tubes, and pipes in electrotechnical usage (paper or cotton as reinforcement in sheets made of phenol- or melamine-formaldehyde resins). In 1896, for example, airplane seats and fuel tanks were made of natural fibers with a small content of polymeric binders [1]. 

Arboform, a composite of lignin, hemp and flax developed by the Fraunhofer Institute, is proposed to replace more traditional materials in the automotive industry. 

EAC Technologies (of Belgium) produces mats of flax, hemp or jute and composites made of flax, hemp or jute reinforced polypropylene. 

As Indian hemp was charred for increasing periods of time, some loss of chemical structure was incurred (Figure 7). The sample charred for 30 minutes is white and fragile, while the 10 and 20 minute samples are still black and fibrous and appear more like the charred fibers observed in the archaeological textiles. It is obvious that the composition has been altered by exposure to heat. The cellulose is dehydrated with the 2900 cm-1 band reduced in each of the levels of charring. The 10 and 20 minute samples are similar to each other, but somewhat different from the uncharred Indian hemp. The 1630 cm-1 band in the uncharred fiber is shifted to 1582 cm-1 due to dehydration. The new bands in the region of 1450 cm-1 and 1200 cm-1 in the 30 minute sample are comparable to those noted by Ercin and Yurum (44). 

Indian hemp [N.A. plant] fibers, charred and uncharred, 61-64/ Inductively coupled plasma-mass spectrometry (ICP-MS) and ICP-OES chemical analyses, Philistine potteiy, 402-411 correlation to LA-ICP-MS elemental analysis, Matisse bronze sculptures, 343-346 Olivella biplicata shell compositional chemistry, geographic patterning, 170-180 prehistoric textiles, 29,35 Roman Carthage curse tablets, 319, 332,333/... 

Use of fibers as reinforcements to make composites is, of course, well established. These are structural applications where, because of the characteristically long length of fibers, they are incorporated in a continuous medium, called the matrix. We describe some of these applications in subsequent chapters in more detail. Yet another common use of fibers of various kinds is in making ropes. In prehistoric times, ropes were made of braided leather strips and vines. Later, vegetable fibers such as jute, hemp, etc., were used to make ropes. More recently, ropes have been made of synthetic pol3nmers and metallic fibers. Ropes can be made by a variety of construction methods twisted, braided, plaited, parallel core and fiber, and wire rope. 

Hemp (Marijuana, Cannabis sativa). Hemp seed oil has an interesting fatty acid composition. One report gives the followimg values palmitic (4—9%), stearic (2-4%), oleic (8-15%), linoleic (53-60%), a-linolenic (15-25%), y-linolenic (0-5%), and stearidonic acid (0-3%). The oil is being used in cosmetic formulations (116). Evidence from a study in Finland indicates that dietary consumption of hemp seed oil leads to increased levels of y-linolenic acid in blood serum (117). The growing of hemp is banned in the United States, and therefore, hemp seed oil must be imported into that country (118-119). 

Hemp Oil Canada Inc. (2004) Nutritional Composition. Available http //hempoilcana-da.com/compo.html. 

Recent investigations of hemp seed oil (5, 11, 12) reported similar findings in fatty acid compositions. The n-3 fatty acid, a-linolenic acid, was determined to constitute between 15.1% and 19.4% of total fat (Table 2). Gamma-linolenic acid (18 3n-6) was also detected in two of the studies, and comprised up to 3.6% of total fatty acids (11, 12) (Table 2). The most prevalent fatty acid was linoleic in all of the studies, which was between 53.4% and 60.0% of total fatty acids and was followed by a-linolenic, oleic, palmitic, y-linolenic, and stearic acids. Eicosadienoic, arachi-dic (20 0), and behenic (22 0) acids were also detected in small quantities. 

Note (l)The content of the hemp coal shows an.addit ional percent. (2)The line under figures shows the composition which continues burning even under 10 a of water. 

Potassium bichromate promotes the burning reaction of potassium perchlorate composition when it is added to it in small amounts. For example, a test showed that the burning rate of a composition which consisted of potassium perchlorate and hemp coal in a weight ratio 75 25 increased 1.55 times when k 3% potassium bichromate was added to it. 

This gains its name from its appearance as a charcoal ball. This is manufactured by coating a black powder type composition many times on an ordinary and rather small shell. During the coating process pieces of hemp are wound around the sphere for reinforcement. This is quite labour intensive, but the effect is very pretty(Fig.8). The fuse of this shell is apt to misfire due to the absorption of moisture during coating, and some device is necessary to avoid this. 

These items are also described in Lancaster s book on page 106, They are so named because the fire dust sparks drop to remind us of waterfalls. They are prepared as follows(Fig.129) Charge a waterfall composition which contains aluminium powder of relatively large flakes into strong paper tubes which have a thin wall which burns away. (See also 15.10.) Put a quantity of ignition composition in the end of each tube. Make holes in it from the outside and pass a piece of wire which is wound with a piece of powder pasted paper through the hole. Fix the waterfall units made in this way to a hemp rope at intervals of about 50 cm. Connect the igniting ends with a line of piped quick match. 

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